Touch sensitive devices are popular as input devices to various computing systems and other devices due to their ease of use and versatility. A touch sensitive device generally includes a touch surface which may, in various applications, be a clear translucent or opaque. In many applications (e.g., smart phones, smart watches, touch-screen tv and touch-screen monitors) a clear touch surface includes a display device that enables a touch interface which, through appropriate software and hardware, allows a user to interact with the display. In other applications (e.g., touch pads) the touch surface does not include a display device that is viewed therethrough. Many methods and apparatus are known for measuring the touch deltas (e.g., the measurable change (i.e., response) resulting from a touch) and from those measurements, determining the location of one or more touches, see, e.g., U.S. Pat. No. 9,019,224 entitled LOW LATENCY TOUCH SENSITIVE DEVICE, and U.S. Pat. No. 9,529,476 entitled FAST MULTI-TOUCH POST-PROCESSING, the disclosures of which are incorporated herein by this reference. Touch delta is usually expressed as a ratio in dB. Generally, the touch delta directly affects the signal to noise (SNR) for the system. In a typical capacitive touch sensor design, high touch deltas are desirable at the touch surface of the sensor. Generally, a touch delta would reflect a difference between a baseline response of a touch sensor and its response with a touch object (such as a finger or stylus) present. In the context of the above-identified patents, a touch delta would reflect a difference between a baseline response of a touch sensor at each given frequency and its response at those frequencies with a touch object (such as a finger or stylus) present.
Portions of a touch sensor—which may be conductive materials such as ITO or silver nano-wire—are embedded in, placed on, or integrated with a touch surface (such portions of a touch sensor may be referred to herein as e.g., touch sensor conductors, conductive elements or touch sensor antennas). Touch sensor conductors are typically placed in a grid of rows and columns, either the rows or columns may be stimulated with signals or energy, although in some embodiments, both the rows and columns are stimulated. In a typical touch application, spacing between the rows and spacing between the columns is generally uniform, and is often proposed in the range of 4 mm to 5 mm.
As used herein, driven conductors are sometimes referred to as drive lines, and the other are referred to as sense lines. (In some touch sensors, the touch sensor conductors may act as drive lines and sense lines at the same time, see, e.g., U.S. patent application Ser. No. 14/216,791 entitled FAST MULTI-TOUCH NOISE REDUCTION, the disclosure of which is incorporated herein by this reference. Touch surfaces such as those described above include an array of touch regions or nodes formed at the crossing points between rows of drive lines and columns of sense lines. To sense touch on the touch surface, drive lines are stimulated causing them to capacitively couple with the crossing sense lines. Receivers measure the coupled signals on the crossing sense lines. In some implementations, coupled signals from nodes proximate to a touch decrease on the sense lines, and vice versa. It should be noted that the word touch as it is used herein does not require physical touch (e.g., actual contact), but only a nearing sufficient to create a measurable touch delta. In general, a touch sensitive device detects the position of touch deltas caused by a touch (i.e., a touch event) by correlating the receivers detecting the touch delta with a row-column position.
Although the rows and columns are identified as “crossing”, the crossing is observed from a plan view. In general, the rows and columns do not touch, rather, they are in close proximity with each other and thus, can be capacitively coupled. In some implementations, the rows and columns are on separate layers. In some implementations, the rows and columns are on separate sides of a substrate. The rows and columns can be placed on the same layer, but can be bridged at each “crossing,” requiring a large number of such bridges. As an example, typical spacing between the touch sensor conductors is between about 4 mm and 5 mm. Thus, on a typical smart-phone, there may be 20-30 rows and 10-20 columns, requiring between 200 and 600 bridges depending on the phone size and inter-conductor pitch.
In many instances, shielding may be required to separate row conductors from column conductors as they are being routed from the touch surface to, e.g., the drive circuit and sense circuit. In the case of generally rectangular touch surface, the rows (e.g., drive lines) must be routed from an edge that is at 90-degrees with respect to the edge from where the columns (e.g. sense lines) are routed. In view of the modern trend to reduce bezel size, attaching the rows and columns to the drive and sense circuits may require careful shielding and/or difficult or circuitous routing.
There is a need for a touch sensor that addresses these shortcomings and provides other benefits.